in "wish you were here" lesson i see the rhythmic pattern in the begining and i play it but how do i know which is an upstroke and which is a downstroke?, i know its a silly question but i just dont know how tell if its upstroke or downstroke , please help me.

I haven't tried to play the song, but I'd be inclined to start by playing all the lone chords (those not joined to anything by a bar) as down strokes.
The chords joined by the bars at the top would be considered as 4 chord strokes, starting with down - so down up down up. As the third position is not filled (the note at the second position is twice as long to make up), I would "dummy" a down stroke and play down up up.

I've just played the MP3 from the lesson and David Hodge plays it the same way.

In Davids lesson when switching from the C to Am he strums the C a few times then does a run on the 3rd fret A string to the 2nd fret A string and on to the Am. This is pleasing to my ear. What other runs can you do? Is he using part of a scale? If so which one? Here's the tab

d duud dud(change) so I change chord on the last down, but when I hear Dave's lesson, it's songs more as

d duud duud(change) on the last d, so which is it?

Thats the way I play it. The last down in your pattern is the first strum of the next chord. So each chord is D DU UD DU. The last up is kind of a cheat to give you time to get to the next chord so just catch the 2 or 3 treble strings.

They are in the lesson. Each verse and chorus has options on how to play it like straight strumming or some single notes added for flavor. And the sections of the song are also in order in the lesson. The straight strumming is good when you are playing with someone else and they are playing the melody and the mixed version are good when you play alone.